1. Field of the Invention
The present invention relates to tool abrading and sharpening apparatuses and, more particularly, is directed to fixtures for holding blades, tools, etc. in an abrading or sharpening position on a grinding device that utilizes abrasive grinding mediums.
2. Description of the Invention Background
A number of modern tools and machines include portions having engageable edges which must be kept free from surface imperfections such as, for example, burrs, nicks and gouges, so that the tool or machine can function properly. For purposes of the present disclosure, such an operation will be referred to as "grinding". Such tools which should be free from surface imperfections include, for example, flat-head screwdrivers, chisels, gouges, the cutter members of planes, spokeshaves and scrapers, and the knife members of planer machines and jointer machines. With respect to those tools which are used to remove wood from a workpiece, the presence of such surface imperfections can mar or gouge the wood surface, requiring additional time and sanding operations to obtain an acceptable appearance for the workpiece.
In addition to the removal of surface imperfections, a number of tools and machines include edges which must be kept sharp so that the tool or machine can properly cut or remove a material of interest. For purposes of this disclosure, the operation of providing a tool with a sharp edge will be referred to as "sharpening". Such tools which must be kept sharpened include, for example, all types of knife tools, woodworking chisels and gouges, and the knife blades of planer machines and jointer machines. The action of either grinding or sharpening, as well as any other activity where material is removed from a surface, will be referred to herein as "abrading".
Perhaps the most rudimentary means for maintaining an edge free from burrs and nicks and/or to sharpen the edge is to use a stone surface, known as a whetstone, oilstone or a bench stone. Such stones may be composed of natural stone or artificial material such as silicon carbide or aluminum oxide, and come in a variety of grits. By repeated stroking of the worn edge on the stone at the proper angle, material is abraded from the edge surface. To remove surface imperfections from the edge, or to straighten the edge, a stone having a coarse or medium grit size is used. To sharpen to the edge, a stone having a relatively fine grit size is employed. To properly sharpen an edge, oftentimes both procedures must be employed so that gross surface imperfections are first removed from the edge using a medium or coarse grit stone, and then the edge may then be sharpened using a relatively fine grit stone.
When sharpening an edge by subjecting the edge to one or both of the above abrading steps, a constant angle should be maintained between the tool and the abrading surface so that the edge is not sharpened in a rounded configuration. Maintaining a constant angle when sharpening by hand using a stone is quite difficult, in part because the tool must be stroked across the stone surface while maintaining substantially constant pressure between the edge and the stone.
To hasten the removal of material from the edge to be maintained and also to aid in maintaining a proper angle between the tool and the abrading surface, a variety of motor-driven grinding and sharpening devices are available. These devices may be capable of either grinding or sharpening, or may provide both features. Many of these abrading devices employ a wheel of a natural or synthetic abrasive material which is driven to rotate by an electric motor.
One such device is the Model GGM-250W grinding/sharpening machine distributed by Reliant, which incorporates an 80 grit grinding wheel which rotates on a horizontally-disposed axis, hereafter referred to as a "vertical grinding wheel", and a water-fed 800 grit sharpening wheel which rotates on a vertically-disposed axis, hereafter referred to as a horizontal sharpening wheel. Reliant is a tradename of Trendlines of Chelsea, Mass. Individual tool rests consisting of flat metal pieces are attached adjacent each wheel for resting the tool which is to be ground or sharpened thereon. The tool is placed on the tool rest and manually moved therealong to ensure the entire tool edge gets sharpened. This method of supporting the tool relative to the grinding wheels is fraught with many problems. In particular, because the tool is manually restrained on the tool rest during the sharpening process, the uniformity of the sharpened edge is entirely dependent upon the operator's ability to uniformly introduce the entire edge to be sharpened to the abrasion surface. If the operator applies more pressure to one portion of the edge, that portion may have more material removed therefrom. In addition, often times during the sharpening operation, if the tool is not uniformly introduced to the abrasion surface, the tool will "kick back" away from the grinding wheel thereby endangering the operator and others that may be located in the surrounding area. Also, because the tool rest of the Reliant machine comprises a flat metal strip supported at its terminal ends, the strip may bow if the tool is pressed onto it with sufficient force. The bowing of the strip will affect the elevation and angle of the blade relative to the abrading surface and may also affect the pressure exerted on the abrading surface by the edge being sharpened. American Machine & Tool Co., Inc. ("AMT"), Royersford, Penn. and Woodtek Machinery, which is a tradename of Woodworker's Supply of Albuquerque, New Mex., distribute grinding/sharpening machines which are similar in design as the Reliant machine and, thus, have the same disadvantages as the Reliant machine.
In addition to the above devices, Makita Electric Works, Ltd., Aichi, Japan, distributes a Model 9820-2 sharpening machine which includes a single sharpening station having a 1000 grit, water-fed, horizontal sharpening wheel. Disposed adjacent the wheel is a tool rest including a support rail having a surface for accepting a tool holder for sharpening.
The tool holder comprises a plate member adapted to be movably supported on the support rail. The blade to be sharpened is positioned on the plate member by four "forward adjust" screws that are threadedly attached to the rear portion of the plate member. A blade clamping plate is secured to the plate member by four blade fastening screws that are threaded into the plate in a position that is somewhat perpendicular to the forward adjust screws.
To position the blade on the tool holder, the forward adjust screws are unscrewed to permit the heel of the blade to contact the blade fastening screws. The blade fastening screws are then lightly tightened and the holder is then placed on the support rail. The right forward adjust screw is then advanced until the right upper edge of the blade contacts the grinding wheel. Thereafter, the far right fastening screw is tightened. The holder is then slidably positioned on the support rail such that the left end of the blade is above the grinding wheel. The left forward adjust screw is then advanced until the left upper edge of the blade contacts the grinding wheel. Thereafter, all four blade fastening screws are tightened.
Thus, the Makita blade holder discussed above requires two adjustment screws to be adjusted to position the blade on the plate such that the blade is properly oriented relative to the grinding wheel when the blade holder is received on the support rail. Such blade adjustment arrangement is time consuming. In addition, there is no means for automatically retracting the forward adjust screws to accommodate wider blades.
As such, there is a need for a tool holder that can be used in connection with an abrading apparatus for safely and accurately supporting and orienting the tool relative to the abrading or grinding medium such that the tool can be uniformly sharpened along its entire length and can be easily adjusted to accommodate a variety of tools of various sizes.